This invention relates to the field of keyswitch assemblies and, more specifically, to keyswitches used in keyboards having compact requirements.
Small portable computers or xe2x80x9cpalmtopsxe2x80x9d can be conveniently carried in a purse or coat pocket. Recent advances in shrinking the size of electronic components, and the rapid growth of the wireless data infrastructure will allow these devices to be conveniently carried and used as portable e-mail machines. At the same time, mobile phones are becoming Internet capable, so can also be used to send and receive e-mail.
Powerful and versatile as these devices are becoming, their use is greatly limited by non-existent or inadequate keyboards. Palmtops which rely on handwriting recognition have proven to be awkward, slow and error prone. Phone keypads are very slow when used to enter text. Keyboards with calculator type xe2x80x9cchickletxe2x80x9d keys (e.g., the Zaurus organizer, made by Sharp Electronics) or membrane keys (e.g., microwave oven keys) also slow down typing and suitable only for thumb or index finger typing of short messages.
Voice recognition suffers from frequent errors and creates a lack of privacy and disturbance to others when other people are near the speaker whose voice is being recognized.
Keyboards found in high quality notebook or laptop computers allow the user to comfortably, privately, and quickly xe2x80x9ctouch-type.xe2x80x9d They have a number of desirable features in common. Importantly, the keyswitches are designed to provide sufficient xe2x80x9ctravelxe2x80x9d (i.e., the distance the key moves when it is pressed), and tactile feedback (i.e., an over-center buckling action), that signals to the user that the key has been pressed sufficiently. When users type quickly with all fingers, they often strike the keys off center. To prevent the keys from binding, high quality keyswitches use mechanisms that keep the key caps parallel to the base as they are pressed. This allows the keys to be struck on any portion of their surface and at non-perpendicular angles to the direction of depression.
It would be highly desirable in many situations to provide keyswitches which have all the features of the best laptop computer keyboards, yet can be stored in a very thin collapsed position. This would allow the creation of handheld computers and mobile phones with built in keyboards suitable to comfortable and fast touch typing. It would also allow the creation of accessory keyboards suitable for comfortable and fast touch typing that can be folded to very small sizes.
Efforts have been made to provide keyboards that contain these features, yet have keyswitch mechanisms that are low profile. Some keyswitch designs only slightly reduce the compactness of a keyboard. One such design, illustrated in FIGS. 1A and 1B, utilizes a rubber cone as a spring mechanism and to provide tactile feedback. A problem with such a design is that the levers have substantial thickness to accommodate a shaft and pivot holes at the central part of the levers to allow pivotally movement in a traditional scissors arrangement. As such, the overall thickness of a collapsed keyswitch using such a design may not be significantly reduced. Another problem with the use of a rubber cone is that it may need to be glued to the assembly with an adhesive. A glued spring may result in inaccurate positioning of the cone and/or adhesive spilling over into unwanted areas.
Another compact keyswitch design, illustrated in FIG. 1C uses a gear mechanism to maintain parallel movement of its linkages. It needs a shaft and pivot holes at the center of its gears. The overall thickness of a collapsed keyswitch is thus limited by the diameter of the gears.
Another compact keyswitch design, illustrated in FIG. 1D utilizes a spring mechanism positioned on the ends of interlocking plates, rather than underneath the plates. However, the thickness of this mechanism when collapsed is limited because the levers have flanges on their sides. The flanges are typically used for stiffening of the lever material and to facilitate attachment to the cap. Such a design may only be able to reduce the thickness of the keyswitch in the depressed position (e.g., when used in a foldable keyboard) to around 4 millimeters (mm). Also limiting the collapsed thickness is the fact that the width of the springs is perpendicularly oriented with respect to the levers.
Yet another drawback to this design is that it may be difficult to assemble. Such a design may require a mounting method that spans multiple layers. A circular extruded feature protrudes downward through the membrane switch layer and base metal layer. It then gets swaged to secure the scissors assembly. This is a disadvantage when trying to achieve a thinner design and also limits the flexibility between layers. Each layer must take into consideration this intrusion. In addition, such a mechanism may have to be machine assembled because metal must be bent or swaged to secure the assembly.
The present invention pertains to a keyswitch. The keyswitch may include two legs interleaved together without a pivot point approximately central to the legs. In one particular embodiment, the sides of the legs may not have flanges and/or hems. In another embodiment, the legs may be undulated at approximately their centers. In yet another embodiment, the keyswitch may also include a spring to engage at least one of the bottom surfaces of the legs.
In one exemplary embodiment, the legs of the keyswitch may each have two lower protrusions on one of their ends and upper protrusions on their other ends with the lower protrusions of one leg disposed between the lower protrusions of the other leg. The keyswitch may also include a base having retaining clips with each of the lower protrusions of the legs pivotally engaged with a corresponding retaining clip. The keyswitch may also include a cap having tabs that may be pivotally coupled with corresponding slots in the upper protrusions of the legs.
In one particular embodiment of the invention, the mechanical action of the keyswitch is designed to feel virtually the same as a high quality laptop computer keyboard so the user can touch-type quickly and comfortably with no learning required. Key travel (the distance the key moves when pushed down) may be approximately 3 mm. When a key is pressed there is also an over-center xe2x80x9cbucklingxe2x80x9d of a spring to create tactile feedback similar to the feedback provided by high-quality keyboards. As such, the keyswitch may provide similar benefits and features of high quality keyswitches as used in laptop or notebook computers, in particular, sufficient key travel, parallel key movement, and tactile feedback. In addition, the keyswitch may be stored in a compressed position of very small thickness that allows it to be used in folding keyboards that may be incorporated into portable devices such as handheld computers and mobile phones.
Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.